This invention relates in general to apparatus for cutting and placing tows of resin impregnated composite materials directly on a tool or mandrel and in particular to such an apparatus which provides a means for cutting the tows to a precise and constant width and storing them in a cassette. The cassettes of tows are then loaded into a fiber placement apparatus for placing the tows at a controlled low tension on a tool or mandrel without gaps between the tows or overlapping tows on the tool.
The present systems for applying tows to a mandrel or stationary tool are totally dependent on the quality of the raw tow material supplied. Using current tow manufacturing processes, it is extremely difficult to produce tow material of constant width with a constant degree of resin tack. If the tows are wider than the nominal width, they will be overlapped in the process of applying them to the tool or they may cause jamming of the mechanism of the tow dispensing head. If the tows are narrower the nominal dimension, gaps will occur between the tows. These overlap and gap conditions result in a composite structure that is not uniform in size, shade or integrity, Another problem of the present systems is that of resin buildup on the tow-handling parts of the machine resulting in frequent stopping of the process for cleaning excess resin from the machine. Resin is also a problem in de-spooling the tow material. It may tack to its underlying tows thus fraying them as material is dispensed from the spool. Yet another problem exists in the present apparatus for fiber placement. This problem is that presented by the necessity to cut individual tows during the lay-up process and restart individual tows according to the contour and cross section of the part to be fabricated. Today's apparatus cuts an individual tow at generally a right angle to the direction of tow movement. Thus a gap is formed at the end of the tow and another gap is formed when the tow is restarted. Ideally, the tow should be cut to the exact form of the opening between its adjacent tows in the lay-up thus avoiding gaps and overlaps. Finally, the present systems apply excessive tension on the tows when they are being placed on a tool having concave surface areas causing them to bridge across a portion of the surface of the tool rather than adhering to the tool surface.